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Monday, January 23, 2017

Fifteen Back Iissues of "Hambrew Magazine" (from the 1990s) Available Online

They look very interesting.  I saw an article by Wayne Burdick.   Doug DeMaw was involved.  Thanks to Tim at Arrow Antennas for making these back issues available.

You can download the .pdf files here:

Sunday, January 22, 2017

HB2HB: N6ORS, W0PWE (and me!)

This is so cool.  Jerry W0PWE has built a magnificent BITX.   With a digital VFO and Termination Insensitive Amplifiers, I think it qualifies as BITX DIGI-TIA #2.   Running it "al fresco" he was tuning around on 40 and he heard DIGI-TIA #1 (mine!).  As soon as he finished soldering in the power amplifier, he put it on the air and, in his second contact, worked Keith N6ORS -- Keith was running his MIN-X rig.  Clearly TRGHS. Great work Jerry!
Hello Bill,
Jerry here W0PWE in Iowa. I save up your podcasts and listen to them when I travel. A year or two ago you and Pete got me interested in the BitX and I finally took action. I have plenty of other
projects I should finish but boy was it ever fun to start a new one. This morning I soldered the
last part in my newly hatched Bitx, drug it over to the operating position and had two great QSOs
with it. See attached photo shows the rig as it was during those QSOs.

When I finished my first QSO with W9SX, Keith in WI N6ORS called me. He was running a multi-band Bitx he had built and we had a great HB2HB qso. Awesome!

My rig is scratch built, mostly SMT and generally follows the 40M schematic that Farhan has on
his HFsignals page. I am using the Kopski/Hayward TIAs though and I designed a 6 pole crystal
filter for it since 6 of the 10 crystals I bought were very similar when I characterized them
with my PHSNA setup. It uses the Adafruit SI5351 board and I modified a sketch that LA3PNA wrote for the Arduino. 

I designed and fabricated the boards for it using the software and process described by K7QO and
W5DOR. Toner transfer with the Hammerhill Gloss paper is working great. The heatsink on my IRF510 is a little light. I could smell the MOSFET warming up during a few of my lengthy transmissions with Keith.

Now the SWL report. While listening on the receiver portion of my Bitx last week I heard you on
7260 at about 0030Z. I think that was Tuesday or Wednesday. I wished I could give you a call but
at that point my PA was merely a few traces on the computer screen. Hope to hear you again on

Jerry - W0PWE

Thursday, January 19, 2017

AB1YK's FB "Al Fresco" Scratch-Built BITX 20

Mike AB1YK built this very nice BITX20.  On a board, al fresco.  Very nice.  He provides a good write up here:

I feel obligated to defend his poor analog VFO.  Mike -- that oscillator never had a chance OM!   You need to nail that coil and that capacitor down!   You threw in the towel and went over to the dark side way too fast.  Go back and get that VFO stable. 

Similarly, I'd say it is time to put away the keyboard and get out the microphone. This is a 20 meter phone rig after all.  Allow it to send your dulcet tones across the seas!

But seriously, great job Mike.  There are very few scratch-built homebrew SSB rigs on the air these days.  Congratulations OM.

Wednesday, January 18, 2017

N8NM's SAVED VFO 30 Meter Rig

In early December Steve Murphy N8NM picked up this "mystery box" at a hamfest.   Dr. Juliano identified it as an old CB VFO.  Even though Steve is deeply committed to the dark side of frequency generation (digital synthesis) I was able to convince him to put this VFO to legitimate and proper amateur radio use AS AN ANALOG VFO.  I mean just look at that dial!  It would be a sin to connect that beautiful mechanism to a rotary encoder.   We see the results below.


The 30m rig that I had hoped to have QRV for SKN is finally ready to hit the airwaves!  I still have a few odds and ends to tidy up, but it's essentially done.

Where I ran into problems was my original choice of IF and VFO frequencies: I'd gone with a 13.51 MHz IF because I had the rocks, but that put the 3rd harmonic of the VFO right in the middle of the band.  Oops.
Moving the IF to 13.56 fixed that problem, but I still had a spur from that harmonic that needed to be filtered.  At first, it looked like a trap on the output of the VFO would squish it, but it ended up requiring a few extra poles of bandpass filtering to get it below -40 dB/c.  Now we're legal.
Anyway, here's a few pics. The chassis are bent from 22 ga aluminum on my trusty Harbor Freight brake.  They're almost square, they look cockeyed because I still need to make brackets to hold the top and bottom together.  The heat sink is overkill for 5 watts, but it was cheap :-)
Electronically, almost everything between the audio and power amps is straight-up Bitx.  The power amp uses a RD16HHF1 driven by my spin on Farhan's RF-386, and the audio is an LM380 driven by an LM324, with gating between CW and digital mode input handled by a CD4066.  The CW tone generator is based on WB0RIO's "clickless" sidetone circuit, which, while a little complicated, creates perfectly formed CW elements that really sound nice.
I'm still amazed at the stability of the LC VFO; I was monitoring JT65 signals over the weekend and noticed zero drift after warm-up.  To keep it ready to rock, it's powered from the "hot" side of the on/off switch, as is the CW oscillator. 
I can't think of much else to say about it...  It is what it is :-)
73 - Steve N8NM

Monday, January 16, 2017

Of Waterfalls, SDRs, and Homebrew Analog Rigs: Words of Wisdom from W8JI


It happened again today. Conditions were good and I was BOOMING into the NYC area on 40 meters.  40 over.  Everyone liked the signal and said it sounded great.  Except for one anonymous grump who chimed in to say that I was "9 kc wide."  I imagine he was basing this on a quick look at his super-dooper SDR waterfall, without any consideration of signal strength or the characteristics of his own receiver. Sigh.  The Waterfall Police had struck again.  

OM W8JI gives a great description of the pitfalls of this kind of "you're-too-wide-because-my waterfall-says-so" reasoning.  Check it out.  And keep it handy in preparation for your next encounter with the 40 meter Waterfall Police.
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column